A human being has previously produced a huge number of chemical substances, and new chemicals are developed every year. These chemicals are utilized in every aspect of a modern life, and serve in improving a life of a human being. To the contrary, among chemicals, some are released into the environment at a variety of stages such as manufacturing, distribution, use, disposal and the like, and adversely influence on health of a human and an ecosystem through remaining in the environment, and biological concentration due to a food chain, and environmental pollution has become a social problem. Therefore, there is demand for assessing influence of a chemical on a human body and an ecosystem.
When a chemical present in a test specimen to be detected, it is very important to improve a detection sensitivity of a detection system. When only a chemical having a low concentration is present in a test specimen, a test specimen must be concentrated depending on a detection sensitivity of a detection system which is used for detecting a chemical having a low concentration. However, in order to concentrate an aqueous solution such as an environmental specimen, a concentrating apparatus becomes necessary. In addition, when a subject chemical is volatile, a chemical is lost by a concentration procedure in some cases. For this reason, a detection system requiring necessity of concentrating procedure as little as possible, that is, an assay system having a high detection sensitivity is desired.
For detecting a chemical present in the environment, there is an assay system utilizing toxicity response of a yeast cell See, for example, WO 03/018792 and Japanese Patent Publication No. 2003-061676).